Locomotion device on castors

Abstract

A locomotion device on castors including: at least one castor mechanically connected to a sole to roll along a ground, the castor being mounted to rotate about an axis of rolling parallel to a plane of the sole and also about an axis of rotation perpendicular to the plane of the sole; a controllable electromechanical braking device configured to apply a braking torque to the castor that varies according to a braking command received; an inertial unit configured to measure a physical parameter indicative of a steering angle; and a central processing unit programmed to establish the braking command according to the physical parameter measured by the inertial unit and to transmit the established braking command to the braking device to apply to the castor a braking torque that varies according to the steering angle.

The invention claimed is: 
     
       1. A locomotion device with castors for moving over the ground, the device comprising:
 a footplate extending primarily in a footplate plane and on which at least one foot of a user is intended to be placed when the device is being used by the user; 
 at least one castor mechanically connected to the footplate to roll over the ground, the castor being mounted to rotate about a rolling axis parallel to the plane of the footplate and also about a rotation axis perpendicular to the plane of the footplate; 
 an inertial center configured to measure a physical parameter representing a turn angle, the turn angle being an angle between a longitudinal axis of the footplate and an orthogonal projection on the footplate plane of an instantaneous direction of movement of the footplate, the longitudinal axis being fixed with no degree of freedom relative to the footplate and contained in the plane of the footplate; 
 a central unit programmed to establish a braking command based on the measured physical parameter and to transmit the established braking command to a controllable electromechanical braking device; and 
 the controllable electromechanical braking device configured to exert a braking torque on the castor based on the received braking command. 
 
     
     
       2. The device as claimed in  claim 1 , further comprising:
 a controllable electromechanical turning device configured to turn the castor and cause the castor to pivot about its rotation axis by an angle determined based on a received pivoting command, 
 wherein the central unit is further programmed to establish, at a time of each command to pivot the castor and based on the measured physical parameter at that time, the pivoting command that maintains the rolling axis of the castor perpendicular to the instantaneous direction of movement of the footplate. 
 
     
     
       3. The device as claimed in  claim 2 , wherein the controllable electromechanical braking device and the controllable electromechanical turning device include a common controllable electrical actuator configured to cause the castor to pivot through a predetermined angle about its rotation axis in response to the pivoting command. 
     
     
       4. The device as claimed in  claim 2 , wherein a shortest distance between the rolling axis of the castor and the rotation axis of the same castor is greater than or equal to 1 cm and the central unit is programmed to establish at a time of each command a pivoting command that additionally maintains the rolling axis of the castor in front of its rotation axis in the instantaneous direction of movement of the footplate. 
     
     
       5. The device as claimed in  claim 2 , wherein the controllable electromechanical turning device includes:
 a sprocket fixed with no degree of freedom to the castor and mounted to rotate about the rotation axis of that castor; 
 a lead screw meshing with the sprocket and extending parallel to the plane of the footplate; and 
 an electrical actuator configured to cause the lead screw to turn through a particular number of turns determined from the pivoting command received to cause the castor to pivot through a corresponding angle about its rotation axis. 
 
     
     
       6. The device as claimed in  claim 1 , wherein the controllable electromechanical braking device includes:
 at least one pad movable between an advanced position to exert pressure on the castor to brake the castor and a retracted position to exert no pressure or a lower pressure on the castor; and 
 a mechanism configured to transform pivoting of the castor in one direction about its rotation axis into a movement of the pad from its retracted position to its advanced position and pivoting of the castor in the opposite direction about its rotation axis into movement of the pad from its advanced position to its retracted position. 
 
     
     
       7. The device as claimed in  claim 6 , wherein
 the controllable electromechanical braking device includes a return member configured to continuously exert a force that returns the pad to its retracted position, and 
 the mechanism configured to transform pivoting of the castor into movement of the pad includes: 
 a cable attached at one end with no degree of freedom to a fixed anchor point on the footplate and at the other end to the pad, and 
 at least one pawl movable by the rotation of the castor between: 
 an eccentric position in which it tensions the cable and thus causes the movement of the pad from its retracted position to its advanced position against the return force of the return member, and 
 an aligned position in which the cable is relaxed and therefore allows the pad to be moved from its advanced position to its retracted position by the return force of the return member. 
 
     
     
       8. The device as claimed in  claim 1 , wherein the controllable electromechanical braking device includes:
 at least one pad movable between an advanced position to exert pressure on the castor to brake the castor and a retracted position to not exert any pressure or a lower pressure on the castor; and 
 a controllable electrical actuator mechanically connected to the pad, and configured to exert on the pad pressure in the direction of the advanced position equal to a braking set point contained in the received braking command. 
 
     
     
       9. The device as claimed in  claim 1 , wherein the central unit is programmed so that the braking torque exerted by the controllable electromechanical braking device on the castor increases as the absolute value of the turn angle increases. 
     
     
       10. The device as claimed in  claim 1 , wherein
 the inertial center is further adapted to measure a physical parameter representing an angle of inclination of the footplate, the angle of inclination being the angle between the plane of the footplate and the instantaneous direction of movement of that the footplate and 
 the central unit is further programmed to establish the braking command based on the measured physical parameter representing the inclination angle, the braking command established based on the physical parameter representing the inclination angle corresponding to a braking torque that increases as the absolute value of the inclination angle increases. 
 
     
     
       11. The device as claimed in  claim 1 , wherein the locomotion device is directly transportable by the user. 
     
     
       12. The device as claimed in  claim 1 , further comprising:
 two footplates mechanically independent of each other, a respective foot of the user being intended to be placed on respective of the two footplates when the device is being used by the user; and 
 fixed to each footplate, at least one of the at least one castor, one of the controllable electromechanical braking device, one of the inertial center, one of the central unit, and a transceiver configured to enable communication between the central units fixed to each of the footplates.